We are investigating the role of the cytoskeleton in malignant transformation using normal and transformed tissue culture cells. We are studying the degree of polymerization of tubulin and actin in these two types of cells using biochemical and ultrastructural methods. Our results to date suggest pronounced differences in the organization of these two proteins in normal and transformed cells and this has led to an investigation of possible differences in the content of actin and microtubule associated proteins in normal and transformed cells. This is done by isolating intact microtubules and microfilaments and analyzing the associated proteins on two-dimensional polyacrylamide gels. Intermediate (100 A) filaments are also being studied as they appear to comprise a great deal of the cytoskeleton in many cell lines. It is hoped that the cytoskeletal "associated proteins" will prove to be those that control the polymerization and orientation of cytoskeletal fibers.